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Homework Help: Determining if decay is possible

  1. Apr 20, 2009 #1
    Determine if decay of U (A-236 Z-92) -> U (A-235 Z-92) + n is possible

    mother -> daughter equations for alpha, beta, or gamma

    I really don't know where to start. I have a few problems to prove like this but no examples. I understand how to caluclate the binding energy and how much energy is released but I don't understand conservation of energy here. Any suggestions are appreciated.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Apr 21, 2009 #2
    What is the total energy of the U (A-236 Z-92)
    and of
    U (A-235 Z-92) + n
    calculated in the restframe of each partile, (i.e. their mass)?
  4. Apr 21, 2009 #3
    Dear Someday, I wish I could do some help.

    Any candidate process satisfies Conservation of energy, momenta and charge. As for nuclear interactions, there's an extra constraint of conservation of mass number. Obviously, in the candidate process
    U(A=236, Z=92) \rightarrow U(A=235, Z=92) + neutron
    the charge and mass number conserve. However, to determine whether this process holds natural and automatical, we need the data of their masses. If
    mass(U(A=236, Z=92)) > mass(U(A=235, Z=92)) + mass(neutron)
    then the interaction is allowed. But I have't the data of U-236, so you have to do it yourself.

    However, I guess, the process in forbiden. because, experiment shows that natural decay of U(A=236, Z=92) is the emitting of \alpha particle (nucleu of Helium, A=4, Z=2).
    U(A=236, Z=92) \rightarrow Th(A=232, Z=90) + \alpha

    1. In nature, U exsists mainly in the form of U-238(99.28%), U-235(0.714%) and U-234(remaining). The three isotopes live together in mineral, and only U-235 is significant in nuclear fissile and atomic bomb. U-236 dosen't exist naturally due to instability, but can be generated via artificial nuclear interactions.

    2. A neutron hits a U-235 nucleu and results in a U-236 nucleu. If the energy of the neutron is properly controlled, the U-236 nucleu could fissile into two light nucleus, and emit 2 or 3 daughter neutrons, which will hit U-235 in neighbourhood and repeat the process above again. This is the dubbed Chain Effect. However, averagely, a U-235 has to absorb 1.175 neutrons to break, so a minor portion of the U-236s will not break immediately, and remian in the nuclear waste.
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